In "the fall of the house of usher," how does the burial of madeline advance the plot of the story

The narrator tells his visit to a childhood friend, Roderick Usher, who owns a house a little strange. This man is sick and tells him to come and cheer him up. He lives with his sister, Lady Madeline, who is also very sick and so he feels very sad.

The narrator spends a season with his friend dedicating himself to talk, read and listen to music. However, one day, Lady Madeline dies, or so it seems. They will leave it in a coffin, in a room in the lower part of the house.

From there, Roderick Usher will gradually lose his head and become sicker and sicker until a stormy night begins to get very upset when he thinks he hears noises throughout the house. To reassure him, the narrator begins to read a book until he also hears those noises, like laments and cries. Roderick Usher, already insane, realizes that they have buried her alive and that is when Lady Madeline appears to them, a fact that precipitates the death of her brother. Before that, and with the imminent collapse of the house, the narrator flees leaving behind the ruins sinking into the lake of the surrounding area.

It is important to emphasize the fundamental role of the house, since its influence on the characters and vice versa is decisive. Also, the negative force that underlies that influence and that leads to the death of the two protagonists and the destruction of the building. That force is immediately discovered at the beginning of the story when the narrator describes his arrival and the feeling of grief and sadness that the vision of the great house produces.

Of course, before this first impression, death is presaged because when you are looking at the house and its surroundings, like the lake and the dry trees, you can only take it as something that is at the end of its resistance to time, just like that of its inhabitants, the last two Usher. It is Lady Madeline, buried alive before her time, who causes the destruction of the house, before her time too, and the death of her brother, to sink all of it into the lake, just as the story ends.

However, what really configures these elements, as many characters as situations and environments, is an extension of the mood, of Poe's mind. This can be seen in the symbology of some of them, such as the house. House that for its character of housing is identified with the body and human thoughts.

it was surely an odd creature that one made up by reading the historians first and the poets afterwards a worm winged like an eagle; the spirit of life and elegance and charm,   in a kitchen chopping up suet. but these creatures, monst'r however entertaining to the imagination, hast no existence in fact. what one might doth to bringeth h'r to life wast to bethink poetically and prosaically at one and the same moment,   thus keeping in toucheth with fact—that the lady is mrs martin, ag'd thirty-six, did dress in blue, wearing a black coxcomb and brown shoeth; but not losing sight of fiction eith'r—that the lady is a vessel in which all s'rts of spirits and f'rces art coursing and flashing p'rpetually. the moment, howev'r, yond one tries this method with the elizabethan mistress, one brancheth of illumination fails; one is did hold up by the scarcity of facts.   one knoweth nothing detailed, nothing p'rfectly true and substantial about h'r.   hist'ry scarcely mentions h'r.   and i did turn to professeth'r trevelyan again to seeth what hist'ry meanteth to that gent.   i hath found by looking at his chapt'r headings yond t meanteth.

wheres the passage with the idiom underlined